There are many hazardous activities that can be made safer by warning people using safety signs. Specific examples include, but are not limited to, signs on snowplows to warn traffic as they approach from behind, slow moving vehicle signs such as are commonly attached to farm vehicles, oversized load signs on the back of highway transportation vehicles, road construction signs, etc.
Necessarily, for a safety sign to be effective, it must be seen by the person to be warned. In certain road safety situations, as listed above, an approaching vehicle's headlights can illuminate the safety signs. However, headlights are not always adequate to provide the necessary warning. Further, there are other applications of safety signs not involving vehicles with headlights, where the person to be warned requires increased visibility of safety signs in poor visibility conditions, from large distances, at night, etc.
Existing configurations of signs that are self lit, such as by incandescent bulbs, have a number of disadvantages. They require large amounts of power to operate. They produce large amounts of unwanted heat. In an application involving snow, in particular, heat can be detrimental by melting snow to water, which may cause electrical failure and/or icing problems. When existing configurations fail, they fail catastrophically. For example, if a rock from a road hits an incandescent bulb, the bulb breaks and fails completely. Also, when an incandescent bulb bums out, it goes from on to off without any warning, or in between condition.
Existing lit configurations also suffer from negative effects of point source lighting. Point sources, such as incandescent bulbs or light emitting diodes (LEDs) provide an intense source of light from a single point. Point sources can cause night blindness after a viewer looks away from the point source light. Also, point source lights appear to flicker and move around when viewed. This is due to their single source beams being distorted by elements such as dust particles, snow flakes, or other elements of the atmosphere between the point source and the viewer. Point source lights also have a limited viewable distance, or penetration through snow, fog, etc. due to similar scattering and distortion of the single source beam.
What is needed is an improved safety sign with high visibility in difficult conditions such as in snow, fog, dust, at night, etc. What is also needed is an improved safety sign without the disadvantages of point source lighting.